Thursday, 30 August 2007
4.PS-102
New findings of alkaline-ultramafic dykes in the Prince Charles Mountains: age and composition
Anatoly A. Laiba, PMGRE, Saint-Petersburg, Russia, Boris V. Belyatsky, Department of Antarctic Geology, VNIIOkeangeologia, Angliisky str., 1, St.-Petersburg, Russia, and Nickolay V. Rodionov, CIR, VSEGEI, Sredniy ave., 74, St.Petersburg, 199106, Russia.
Dikes of phlogopite-bearing alkaline picrites discovered in 2004 in the southern part of Mt. Meredith based on their mineralogical and geochemical composition are comparable to typical mica kimberlites and differ considerably from the well-known alkaline-ultramafic bodies in Jetty Peninsula and along the shores of Radok Lake. However, temperature and pressure estimations of their crystallization (990°C and 18-26 kbar), their age (122 Ma), and primary isotope signatures (87Sr/86Sri = 0.7048-0.7051, εNd = -1.0 to -0.6) indicate that conditions of their formation are similar to those of the Beaver Lake province. Considering these relations and that their formation may be connected with development of the Lambert-Amery rift in Mesozoic time due to mantle-plume activity (Kerguelen plume?) and Gondwana disintegration, we interpret these alkaline-ultramafic bodies to be a single magmatic province, comparable in their age, conditions and composition with the alkaline-ultramafic carbonatite Shillong province in India.